This invention relates to a process for producing polyamine carbamates.
Polyamines have been used as vulcanizing agents for elastomers, especially fluoroelastomers. Unfortunately, low molecular weight polyamines exhibit a number of undesirable properties: they are liquid, they are odorous, and they are corrosive. However, conversion of the polyamines to carbamates alleviates these problems and, therefore, polyamine carbamates have been used extensively as curing agents for elastomers, especially fluorinated olefin polymers and acrylate polymers containing carboxylic acid or reactive chloride cure-sites. Procedures for vulcanizing these polymers with polyamine carbamates are well known in elastomer technology and described in, for example, U.S. Pat. Nos. 3,029,227; 3,088,938; and 3,888,472. Polyamine carbamates are particularly useful as vulcanizing agents because they are solid (being ionic) derivatives of the polyamines, they do not have the disadvantages mentioned above common to polyamines per se, and they dissociate at vulcanization temperatures, e.g., in excess of 100.degree. C., into their components, thus making the polyamine available for vulcanization.
Heretofore, polyamine carbamates have been prepared by dissolving a polyamine in an organic solvent and adding carbon dioxide to the solution. This procedure has been used commercially for the production of polyamine carbamates, but it does have certain disadvantages. Specifically, the solvent and the precipitated polyamine carbamate must be separated and the carbamate dried before it is ready for use. This is an expensive and time-consuming procedure. The present invention is directed to a process that is free from the above-mentioned difficulties and the material, labor and energy costs using the process of this invention are less than that of the generally used abovedescribed commercial procedure.